ProjectSummary: Overthelast30years,spinepainhasbeenthemostcommonreasonforMedicare enrollmentbasedondisability,andallMedicareenrollees?whetherenrolledbyvirtueof disabilityorage?haveincreasinglyusedspinalmanipulationtherapytotreatsuchpain.The AmericanHeartandAmericanStrokeAssociations(AHA/ASA)recommendedthatpatients beinformedofthestatisticalassociationbetweencervicalspinalmanipulation(CSM)and cervicalarterydissection(CAD)butcouldnotarticulatethemagnitudeofthatrisk.The literatureonwhichtheAHA/ASAbasedtheirrecommendationsusedolderdatafromoutside theUSandflawedmethods(inaccurateidentificationofCAD,relyingonpatientrecallto identifyCSM,usingcontrolsthatwereconsiderablyhealthierthancases,andlimitingCSMto thatprovidedbydoctorsofchiropractic,althoughotherpractitionertypesalsoprovideCSM). ToinformMedicareenrollees,providers,andpolicymakersabouttheriskofCSM- associatedCADandtoaddressthelimitationsofpriorstudies,wewillanalyzeMedicare servicesdatafrom2004-2015forbeneficiariesconcurrentlyenrolledinMedicarePartsAand B.WewillusediagnosticcodesspecifictoCADtoaccuratelyidentifycasesandmatchthem topropercontrols,calculatetheannualincidenceandprevalenceofCAD,identifycommon comorbiditiesofCAD,assessoutcomes(includingmortalityandchangesincostsofcare), anddeterminewhetherthereisanassociationbetweenCSMandCAD,byprovidertype.If wefindsucharelationship,wewillcalculatetheriskofCADfollowingavisitforCSM. Toavoidtheselectionbiasthatoccurredinpriorstudies,wewillusepropensity scoringbothtoadjustforthelikelihoodofobtainingCSM(studieshaveshownthatpatients whouseCSMareyounger,healthier,andwealthierthanthosewhodonot)andtomatch controlsoncomorbiditiesfoundtobeassociatedwithCAD.Thoseadjustmentsshould unmaskrelationshipsthatmighthavegoneundetectedinpreviousstudiesduetoa combinationofexposurebias,selectionbias,andrecallbias. Ourpilotworkindicatesthattherewereover3,200casesofCADintheMedicare populationduringthetimeperiodofouranalysis,makingthisthelargeststudyofCADtodate. Policymakers,providers,andpatientswillbeabletouseourfindingsabouttherisksofCSM comparedtoothercommonlyusedtreatmentsforspinepaintomakeinformedfinancingand treatmentdecisions.